A centrifugal switch is already known (German Offenlegungsschrift No. 1 490 452), whose centrifugal pendulum, in the form of a bell crank and secured via a metal band bearing on a revolving carrier element, acts via a contact screw disposed in the extension of the rotary axis of the centrifugal force switch upon a switch contact attached to the housing. In order to reduce wear from friction, the contact screw is centrally disposed in the extension of the rotary axis of the centrifugal force switch, but the centrifugal pendulum rests at every rpm on this contact screw; as a result, there is nevertheless some wear at this point, although it is reduced. The known centrifugal switch serves as an rpm contact governor for electric motors and is not suitable as a means of safety shutoff, upon attaining a shutoff rpm, for fuel injection systems in internal combustion engines which are electrically controlled in an open- or closed-loop manner, especially when used in Diesel engines.
Because of this band bearing, embodied by a leaf spring and secured in the form of a bridge between the carrier element and the centrifugal pendulum, and because the flyweight mass is disposed close to the rotary axis of the centrifugal switch, this known centrifugal switch exhibits a very low increase in centrifugal force when there are small changes in rpm, and the type of freely supporting band bearing used results in an imprecisely defined pivotal bearing point. Because of the slow manner of opening of the contact, there is contact burnoff. The restoring spring, embodied as a tension spring and suspended, inclined obliquely relative to the rotary axis, on the carrier element and on the centrifugal pendulum is so designed that even before attaining the nominal rpm the centrifugal pendulum rests on the contact screw, acting as an actuation pin; as a result, wear at this point is unavoidable. To actuate the movable contact element, the spring forces of both the contact and the band bearing embodied by a leaf spring and the initial tension of the restoring spring must all be overcome, and the effective force for lifting the movable contact element which remains is very small. In the case of soiling of the contacts, when the contacts stick or under external influences such as rotational fluctuations and shocks, further incalculable forces come into play as well; thus it would not be possible, with the known apparatus, to have a precisely maintainable means for safety shutoff upon attaining a predetermined rpm defined within narrow limits. The freely supporting band bearing which bridges the distance between the carrier element and the centrifugal pendulum and which is embodied by a bending spring would also not be suitable for absorbing the rotary acceleration forces occuring in Diesel engines.